The islands have had a unitary authority council since 1890, and are separate from the Cornwall unitary authority. Some services are combined with Cornwall and the islands are still part of the ceremonial county of Cornwall.

Scilly has been inhabited since the Neolithic. Its history has been one of subsistence living until the early 20th century (people lived from what they could get from the land or the sea). Farming and fishing continue today, but the main industry now is tourism.

It is likely that until relatively recent times the Isles were much larger with many of them joined into one island, named Ennor. Rising sea levels flooded the central plain around 400–500 AD, forming the current islands.[2]

Evidence for the older large island includes:

A description in Roman times describes Scilly as "Scillonia insula" in the singular, as if there were a single island or an island much bigger than any of the others.

Remains of a prehistoric farm have been found on Nornour, which is now a small rocky skerry far too small for farming.[3]

At certain low tides the sea becomes shallow enough for people to walk between some of the islands. This is possibly one of the sources for stories of drowned lands, e.g. Lyonesse.

Ancient field walls are visible below the high tide line off some of the islands (e.g. Samson).

Some of the Cornish language place names also appear to reflect past shorelines, and former land areas.[4]

The whole of southern England has been steadily sinking in opposition to post-glacial rebound in Scotland.

Offshore, midway between Land's End and the Isles of Scilly, is the supposed location of the mythical lost land of Lyonesse, referred to in Arthurian literature.

Scilly has been identified as the place of exile of two heretical 4th century bishops, Instantius and Tiberianus, who were followers of Priscillian.[5]

The Isles of Scilly form an archipelago of five populated islands and many other small rocky islets (around 140 in total) lying 45 km (28 mi) off Land's End. They are all composed of granite of early Permian age.

The position of the islands causes great contrasts. The warming effect of the sea means they rarely have frost or snow. This allows local farmers to grow flowers earlier than would grow on mainland Britain. The chief agricultural product is cut flowers, mostly daffodils.

Exposure to Atlantic winds means that spectacular winter gales lash the islands from time to time. This is reflected in the landscape. On Tresco, the lush sub-tropical Tresco Abbey Gardens shelter on the southern end of the island, but the low heather and bare rock get the wind on the exposed northern end.